Conventionally, a vehicle lamp device, particularly, a head lamp, mainly uses a halogen lamp or a High Intensity Discharge (HID) lamp as a light source. In recent years, however, a vehicle lamp device using a semiconductor light source such as a Light Emitting Diode (LED) has been developed.
In order to further improve visibility, for example, JP-A-2004-241142 discloses a vehicle lamp device including a laser diode (also referred to as a semiconductor laser) and a fluorescent substance, instead of an LED. In this vehicle lamp device, an ultraviolet light which is an excitation light emitted from the laser diode is emitted to the fluorescent substance. The fluorescent substance receives the ultraviolet light and generates a white light. The white light generated by the fluorescent substance is emitted to the front of the lamp device such that a predetermined light distribution pattern is formed. In this vehicle lamp device, the excitation light is not emitted to the front.